The image quality of images captured by digital imaging devices such as digital cameras is increasingly important. To achieve increased quality manufacturers has increased the number of pixels captured by the sensor, the light sensitivity, the optics arranged to guide light representing the image to an image sensor of the camera. Another important factor directly affecting the quality of an image captured is the positioning of the image sensor. In order to achieve optimal image quality the image sensor of the camera has to be positioned at a correct distance from the lenses of the optics, otherwise the image will be blurred as it is out of focus. Moreover the image sensor should not be tilted in relation to the optical axis of the lenses of the optics of the camera as such tilt will make the focus vary over the sensor surface.
Hence one contributing factor for achieving high image quality is to position the image sensor correctly. In order to correctly position the image sensor, its position must be checked in order to confirm correct positioning or suggest adjustment of the image sensor position. Today, one of two methods is commonly used in order to check the position of the image sensor.
The first method includes sending a laser beam parallel with the optical axis of the camera onto the image sensor and measuring the angle of the reflection from the image sensor. During the measurement, the lenses of the optics of the camera are removed. From this method, it is not possible to tell whether the distance to the camera optics is the correct distance or not. Moreover, if the surface of the image sensor is not flat and smooth, the accuracy of the measurement may decrease.
The second method includes capturing a target image through a lens, analyzing the captured image, and adjusting the position of the image sensor or the lens as indicated by the result from the analyses of the captured image. This method may advantageously be used for cameras in which the lens is fixedly arranged in relation to the image sensor, as the adjustments based on the analysis also takes into account defects in the lens.